1. Field of the Invention
The present invention relates to a bonding method and apparatus which are used to bond two parts and more particularly to a alignment method and apparatus which align the two parts by correcting any positional discrepancy between the two.
2. Prior Art
When bonding two elements, there are several different ways. In chip bonding, chips are bonded to lead frames or circuit boards. Outer bonding is to bond outer leads of solid devices to lead frames or circuit boards, and in inner lead bonding, chips are bonded to inner leads installed on a tape carrier.
In these bonding methods wherein two elements or two parts are bonded together, it is necessary to detect the positional discrepancy of one part relative to the other by means of detection means and correct the positional discrepancy on the basis of obtained detection results so that the two parts are positionally aligned.
A conventional bonding device in which one part is held by vacuum suction adhesion, conveyed onto another part and bonded there is disclosed in the Japanese Patent Publication (Kokoku) No. 2-26379. In this device, the pattern on one part is detected in the bonding position, while the pattern on the other part is detected in a position which is separated from the bonding position. Then, the part which is held by vacuum suction adhesion and conveyed is conveyed to a point above the other part, so that the two parts are positionally aligned, correcting any relative positional discrepancy between the two parts.
In this prior art device, the positional discrepancy between the two parts is detected with one of the two parts in a position that is away from the position of the other part. Accordingly, when one part is conveyed from the detection position to the bonding position, that is, above the other part, a mechanical operation error, that is inherent in the conveying means, makes it impossible to obtain a high-precision positional alignment of the two parts.